This invention relates to the open-end spinning of yarn, and more particularly to the spinning of yarn using a rotary spinning unit which collects and joins the fibers for twisting into a spun yarn.
The use of a rotating rotor in open-end spinning is generally known to the art. In a typical prior art operation, staple fibers are continuously aerodynamically fed to a rotating spinning rotor where in they are subjected to centrifugal force created by the rotation thereof, causing the fibers to progress outwardly to a point at which the fibers gather, the gathered fibers being continuously withdrawn and twisted to form a spun yarn. Among the advantages of such a spinning operation are increased productivity, decreased labor costs and the potential reduction of power costs. However rotor open-end spinning is subject to several disadvantages, a major disadvantage being the relatively low tensile strength in comparison with conventional ring spun yarn. The decrease in tensile strength stems from the random orientation and the bridging of fibers inherently occurring in rotor open-end spinning resulting in a significant loss of effective fiber length contribution to yarn strength. The most widely used fiber feeding means has been a licker-in disposed to feed the fibers to the rotor unit. The licker-in opens the fibers and partially aligns them through its combing action, but in doing so the toothed wheel of a licker-in itself causes hooks on the ends of fibers which are not straightened prior to the spinning operation, and as a result there has been limited commercial usage of open-end spinning of this sort.
Another significant disadvantage of rotary open-end spinning is the vulnerability of such apparatus to dirt and debris. Fibers fed into the rotor must be very clean because trash entering the rotor will centrifugally travel to and collect at the outer point at which the fibers gather, causing unevenness in the yarn produced and resulting in a higher number of ends down.
Typically, known open-end spinning devices rely solely on the application of aerodynamic forces to accomplish fiber feeding, orienting and aligning in delivering fibers to the rotor, resulting in the aforementioned disadvantages. In an attempt to avoid the problems of aerodynamic systems, Breitenbach U.S. Pat. No. 3,673,781, issued July 4, 1972, discloses the use of an electrostatic field and minimized aerodynamic forces, with the rotor serving as one of the electrodes, but such an arrangement sacrifices the straightening, orienting and aligning advantages of aerodynamic systems in attempting to minimizing the disadvantages.
In another form of known spinning, a core yarn is run through a fiber feeding device and is twisted to form a core yarn. Examples of such core spinning are disclosed in Senturk and Aschenbrenner U.S. Pat. No. 3,845,611, issued Nov. 5, 1974 and Aschenbrenner U.S. Pat. No. 4,028,871, issued June 14, 1977. In these devices electrostatic forces are utilized to straighten and align fibers for effective orientation for deposit on and twisting with a core yarn. These devices do not involve rotor spinning or aerodynamic feeding, however, although Aschenbrenner U.S. Pat. No. 4,028,871 has been known to produce commercially orienting and straightening forces acting on the fibers.
In contrast to the use in the prior art of either electrostatic or aerodynamic forces on a mutually exclusive basis, the present invention combines aerodynamic and electrostatic forces in a unique manner to achieve a commercially acceptable spun yarn of comparable or better quality than conventional ring spun yarns. This is done using electrostatic field producing apparatus, in one embodiment this is the same type apparatus as disclosed in Aschenbrenner U.S. Pat. No. 4,028,871, employed to provide initial straightening and aligning of staple fibers and, in the one embodiment, a final fiber-cleaning step prior to spinning. In this manner, effective fiber length contribution to yarn strength is made possible, a result which does not occur when licker-ins are normally employed with rotary units. The electrostatic force is combined with aerodynamic force that is applied to aerodynamically withdraw the fibers from the electrostatic field and aerodynamically feed them to the rotating spinning rotor at an ever-increasing velocity so that the straightening and linear alignment achieved by the electrostatic field is not only maintained but enhanced. Means are also provided to prevent any fiber distorting decrease in the velocity of the fibers upon entering the rotor chamber. Fibers are therefore deposited onto the rotor surface, which is rotated at a greater surface speed than the fibers being fed thereto, in a straightened and aligned disposition and are centrifugally gathered and combined for twisting and withdrawing therefrom as a spun yarn. In this manner, a high quality uniform spun yarn is produced having a consistently higher average tensile strength than conventional ring spun yarn.